Ultrasonic delay line and method of manufacturing an ultrasonic delay line

ABSTRACT

An ultrasonic delay line comprising a glass body having first and second surfaces on which an input transducer and an output transducer are mounted. A third surface of the body perpendicular to the first two reflects energy towards a fourth parallel surface opposite thereto and fluted to damp the energy received. The transducers are polarized parallel to their respective contact surfaces and parallel to the third surface. The main energy propagation path in the body is parallel to the third surface.

United States Patent Cornells Franx; Mnnlred Franz Karl Glmmel, both 01 Ernmnsingel, Elndhoven, Netherlands lnventors Appl. No. 688,482

Filed Dec. 6, 1967 Patented July 13,1971

Assignee U. S. Philips Corporation New York, NY.

Priority Dec. 28, 1966 Netherlands 6618228 ULTRASONIC DELAY LINE AND METHOD OF MANUFACTURING AN ULTRASONIC DELAY LINE 12 Claims, 6 Drawing Figs.

0.5. CI 333/30, 310/96, 29/2535 Int. Cl "03h 9/30 Field of Search 333/30, 72, 6; 117/217; 29/2535; BIO/969.8

References Cited UNITED STATES PATENTS 4/1950 Arenberg 333/30 3,070,761 12/1962 Rankin 333/30 2,672,590 3/1954 McSkimin 333/30 3,133,258 5/1964 Meitzlcr 333/30 3,300,739 1/1967 Mortley .r 333/72 3,150,275 9/1964 Lucey .1 29/600 3,488,607 1/1970 Bongianni r r .1 333/30 2,965,851 12/1960 May,.1r 333/30 Primary Examr'ner- Herman Karl Saalbach Assistant ExaminerC. Baraff Attorney-Frank R. Trifari ABSTRACT: An ultrasonic delay line comprising a glass body having first and second surfaces on which an input transducer and an output transducer are mounted. A third surface of the body perpendicular to the first two reflects energy towards a fourth parallel surface opposite thereto and fluted to damp the energy received, The transducers are polarized parallel to their respective contact surfaces and parallel to the third surface. The main energy propagation path in the body is parallel to the third surface KPATENTEUJULUIQH 3593213 INVENTORS CORNEIJS FRANX FRED F, K .GAMMEL ULTRASONIC DELAY LINE AND METHOD OF MANUFACTURING AN ULTRASONIC DELAY LINE two further surfaces which damp and/or disperse the ul- 0 trasonic vibrations.

It known per se to provide ultrasonic delay lines with a damping material on those surfaces or portions of surfaces where a reflection of ultrasonic vibrations. for example, ultrasonic scattered radiation, must be prevented. Alternately, said surface may be roughened, for example, by sand blasting, by grinding grooves therein or by forming grooves therein simultaneously with a moulding operation.

The invention is also applicable to a method of manufacturing an ultrasonic delay line, starting from a glass body two surfaces of which are surface-ground and provided with an input and an output transducer. In all these cases considerable manufacturing cost is previously spent prior to being able to start with the finishing operation, for example, regrinding one of the reflection surfaces for the ultrasonic vibrations so as to obtain the desired delay time between the electric signal applied to the input transducer and that generated at the output transducer.

It is an object of the invention to considerably reduce said cost and possibly even the cost of the finishing operation. The invention is characterized in that the body is divided into portions, preferably by a cutting operation, substantially parallel to the direction of propagation of the ultrasonic vibrations and parallel to the two further surfaces referred to in the first paragraph and perpendicular to the surfaces for said transducers referred to in the third paragraph.

By means of the steps according to the invention, it is possi ble to obtain an ultrasonic delay line using a glass body two surfaces of which are provided with piezoelectric input and output transducers polarized parallel to their contact surfaces with the glass body at least one (third) surface of the glass body is parallel to the principal direction of propagation of the ultrasonic vibrations which propagate from the input transducer through the glass body to the output transducer. The delay line is characterized in that the dimension of the body perpendicular to the last-mentioned (third) surface is smaller than the dimensions of this third surface, that the directions of polarization of the transducers are also chosen to be parallel to this third surface, and that the surface of the glass body opposite this third surface reflecting the ultrasonic scattered radiation is formed as a damping and/or dispersing surface for this scattered radiation.

The invention is based on the recognition of the fact that said cut surface acts as a mirror for the ultrasonic waves with the result that the body behaves as if it were twice as thick (measured perpendicularly to this surface) and hence the damping for the desired signal is reduced. The undesired scattered radiation of the ultrasonic waves will be able to strike a damping and/or dispersing surface of the delay body in time, that is to say, before it strikes the output transducer, and as a result be rendered harmless. A further advantage is that said cut surface generally requires no further finishing treatments. Apart from these advantages a considerable economic advantage is furthermore obtained if a plurality of operations can be carried out in one operation at a time, such as melting moulding and simultaneously forming damping flutes or grooves, grinding reference surfaces, grinding of the two surfaces on which the input and output transducers must be provided at an angle accurately determined relative to these reference surfaces, applying electrodes to these surfaces, soldering the said transducers on these electrodes and grinding all delay lines obtained after sawing to have the correct delay time. Already from a point of view of mechanical strength and homogeneity of the glass within each delay line the method according to the present invention is considerably more favorable than it each delay line would have been manufactured separately.

In order that the invention may be readily carried into effect, it will now be described in detail, by way of example, with reference to the accompanying diagrammatic drawing, in which:

FIG. 1 shows an ultrasonic delay line in which the principle of the invention has not yet been realized,

FIG. 2 serves to illustrate the step according to the invention,

FIG. 3a shows the step according to the invention applied to a delay line of the type shown in FIG. 3b, before the cutting operation,

FIG. 4a likewise shows the step according to the invention applied to the delay line of the type of FIG. 4b, delay body before the cutting operation.

FIG. 1 shows a glass body G having two flat surfaces 1 and 2, for carrying an input transducer r, and an output transducer t,, respectively. The material chosen for the glass is preferably of a composition which, under the given conditions, leads to a constant delay time between electric input vibrations applied to the transducer 1, and electric output vibrations generated by the transducer as a result thereof. The glass body G is obtained by placing the molten glass material in a mold having rough surfaces, cooling same to form the rough body, grinding a pair of surfaces 1 and 2 in a proper manner for mounting thereon the input and output transducers t, and I respectively. The transducers t, and l, are preferably manufactured from a thin plate of some piezoelectric material, for example, a lead or an alkaline-earth titanate-zirconate or the like. The largest or main surfaces of the plate are provided with electrodes for supplying and deriving the electric signal oscillations.

The ultrasonic vibrations generated by the transducer will propagate mainly perpendicular to the surface 1 towards the transducer t, Due to the finite dimensions of this transducer as well as to irregularities both in the material of the transducer and in the glass of the body G, the ultrasonic wave emerging from the transducer 1 will, however, also include rays deviating from the principal direction of propagation. The latter rays will be indicated by "scattered vibrations." Surfaces 3 and 4 of the glass body G show a fluting which may be obtained, for example, during moulding of the glass by using a mold in which the substantially parallel rough surfaces corresponding to surfaces 3 and 4 are provided with corresponding protuberances, as a result of which the ultrasonic scattered vibrations striking it are further dispersed and clamped in such manner that these scattered vibrations do not substantially contribute to the ultrasonic waves striking the output transducer 1,.

The step according to the invention consists in that the body G is bisected along a plane perpendicular to the plane of the drawing and passing through the line 5. The result then is that two ultrasonic delay lines G, and G, are produced as shown in FIG. 2. From the ray paths of the ultrasonic vibrations indicated by arrows in FIGS. 1 and 1, it appears that the dispersal and absorption of said undesired scattered radiation has remained unchanged because the surface of division 5 acts as a mirror and therefore reflects the scattered radiation to the fluted surface 3 where it is dispersed in a chaotic manner and undergoes so much damping that only a small portion reaches the transducer r,. However, rays which strike the surface S at a very small angle will be totally reflected by the surface 5 and reach the transducer t, with substantially the same delay time as the rays passing parallel to the surface 5 from the transducer I, to the transducer t As a result the transmission of desired signals involves only slight losses.

In this connection it may be noted that preferably transversely polarized ultrasonic vibrations are used the direction of polarization of which is parallel to the surface 5. To this end the transducers r, and t, are polarized not only parallel to the contact surfaces 1 and 2 of the glass body G but also parallel to the surface 5 and hence perpendicular to the plane of the drawing. in transducer materials as described above remancnt polarization may be brought about in the material by exposing it for some time to a strong electric field, preferably at a high temperature. The dimensions of the body G in this direction, thus perpendicular to the plane of the drawing, are considerably larger than the largest distance between the surfaces 3 and for passing a sufficiently wide bandwidth. Especially for the ultrasonic delay lines with reflection surfaces for the desired ultrasonic vibrations to be referred to hereinafter, this choice of the direction of polarization is unusual because a slight loss occurs at these reflection surfaces which would be prevented if a polarization parallel to the plane of the drawing were chosen. Said direction is therefore chosen to have as much benefit as possible from the reflecting or mirror action of the surface 5 without being hampered (intruded) by energy conversion of the transverse vibrations into longitudinal vibrations, or into vibrations having a different direction of polarization.

FIG. 3b shows a rod-shaped glass body I the long surfaces of which are provided throughout with flutes which may be obtained, for example, by means of a moulding operation. To this end the glass may be moulded in a mould the walls of which have the corresponding fluted structure. The hot glass may also be drawn in the shape of a rod and passed between rollers which are provided with such flutes as to lead to the desired grooves or flutes on these long surfaces. The transducers r, and I, may also be previously arranged with the direction of polarization of said transducers being chosen in the direction P parallel to the contact surfaces 1 and 2, respec tively. By sawing the glass body 0 of FIG. 3b,mainly parallel to two of these long surfaces parallel to the direction of polarization P, namely corresponding to the dot-and-dash line 5, two delay lines are obtained one of which is shown in FIG. 30. By previously mounting the transducers r, and t, which are then also bisected during sawing, twice the number of delay lines may be obtained with any increase of cost which is almost negligible.

FIG. 4 shows a glass body the sectional surface of which corresponds to that described in the prior US. Pat. application Ser. No. 539,l9l filed Mar. 31, i966. The fiat surfaces ll and t2 carry the input and output transducers r, and t,, respectively, and form angles of approximately 45 with a flat end surface 13 which is substantially perpendicular to two flat end surface 13 which is substantially perpendicular to two flat side surfaces 14 and I5, respectively. the lengths of which are chosen to be such that a reflection of the ultrasonic vibrations occurs only twice at these side surfaces. The glass body may also have the shape as described in the prior US. Pat. application Ser. No. 618,!59, filed Feb. 23, 1967. in this case the angle formed between the surfaces 11 and i2 is considerably larger. namely almost 180', no special requirements being imposed on the surfaces 14 and 15. When making flutes on the surfaces 16 and I7 (and possibly on the surfaces 14 and as well as for obtaining the desired positioning of the glass body for grinding at the correct angles the various surfaces important for the ultrasonic propagation the method as described in the last mentioned prior patent application may be adopted. Hy again sawing the glass body G provided with the transducers t, and r, in accordance with the surface indicated by the dot-and-dash line 5, two ultrasonic delay lines are again obtained one of which is shown in FIG. 4a. The transducers r, and r, are once again polarized, not only parallel to the contact surfaces 1] and 12 but also parallel to the surface of division 5, as is indicated by the arrows P.

It is preferable to ensure that the transducers I, and t, directly engage the cut surface 5. This is already automatically achieved by previously arranging these transducers on the glass body G, for example, according to a method described in one of the above prior applications and then sawing them simultaneously with the glass body 0. The surfaces of the transducers r, and t, are then preferably considerably smaller than those of the contact surfaces l and 2 and ll and 12, respectively. with the glass body, so that after sawing the transducers r, and I, still remain separated at a considerable distance from the damping surfaces 3 (see FIG. 2) and 16 and 17, respectively (see FIGS. 4a and 4b).

What we claim is:

l. A method of manufacturing an ultrasonic delay line comprising the steps of forming a glass body having two surfaces for carrying an input and an output transducer and at least two further surfaces adapted to damp and/or disperse the ultrasonic vibrations, and cutting through the body substantially parallel to the desired direction of propagation of the ultrasonic vibrations and parallel to said two further surfaces.

2. A method of manufacturing an ultrasonic delay line, starting from a glass body two surfaces of which are surfaceground and provided with an input and an output transducer, characterized in that the body is divided into portions, preferably sawn, substantially parallel to the direction of propagation of the ultrasonic vibrations and perpendicular to the surface of said transducers.

3. A method of manufacturing an ultrasonic delay line comprising the steps of placing molten glass material in a mold having at least two substantially parallel surfaces provided with protuberances, cooling said glass so that a rough glass body showing two substantially parallel surfaces provided with a fluting corresponding to said protuberances is formed, grinding two other surfaces of said rough glass body substantially perpendicular to said first mentioned two surfaces, securing an input and an output transducer respectively on said two other surfaces, grinding at least one further surface of said glass body substantially perpendicular to said first mentioned two surfaces to reflect ultrasonic rays emerging from said input transducer to strike upon said output transducer, and bisecting said glass body according to a plane substantially parallel to said first mentioned two surfacesv 4. An ultrasonic delay line comprising a glass body having two surfaces which are provided with piezo-electric input and output transducers polarized parallel to their contact surfaces wit the glass body, and at least one third reflecting surface which is parallel to the principal direction of propagation of the ultrasonic vibrations which propagate from the input transducer through the glass body to the output transducer, characterized in that the dimension of the body perpendicular to the last-mentioned third surface is smaller than the dimensions of this third surface, that the directions of polarization of the transducers are also chosen to be parallel to this third surface, and that the surface of the glass body opposite this third surface reflecting the ultrasonic scattered radiation is formed as a damping and/or dispersing surface for this scattered radiation.

5. An ultrasonic delay line as claimed in claim 4, characterized in that it is manufactured of moulded glass.

6. An ultrasonic delay line comprising a solid ultrasonic wavetransmitting body having first and second surfaces, an input transducer and an output transducer in contact with said first and second surfaces, respectively, for propagating ultrasonic vibrations from the input transducer through the solid body to the output transducer along a main propagation path, said body having a third ultrasonic energy reflecting surface parallel to said main propagation path and a fourth surface opposite said third surface and formed as an energy damping sur face for the scattered ultrasonic radiation reflected from the third surface, the dimension of the solid body perpendicular to the third surface being smaller than the dimensions of said third surface, and wherein said transducers are polarized parallel to their respective contact surfaces with the solid body and parallel to the third surface of the solid body.

7. A delay line as claimed in claim 6 wherein said transducers are composed of piezoelectric material and said solid body is composed of glass.

8. A delay line as claimed in claim 7 wherein said glass body is rectangularly shaped and said first and second surfaces are the parallel end faces of the rectangular body.

9. A delay line as claimed in claim 8 wherein a fifth surface of the body that is perpendicular to the first and third surfaces is formed as an energy damping surface.

perpendicular to said third and fourth surfaces.

l2. A delay line is claimed in claim 7 wherein said third surface is arranged to reflect substantially all of the energy impinging thereon and said body dimensions are chosen so that the distance between the third and fourth surfaces is less than the width dimension of the third surface, whereby the delay line exhibits a wide bandwidth 

1. A method of manufacturing an ultrasonic delay line comprising the steps of forming a glass body having two surfaces for carrying an input and an output transducer and at least two further surfaces adapted to damp and/or disperse the ultrasonic vibrations, and cutting through the body substantially parallel to the desired direction of propagation of the ultrasonic vibrations and parallel to said two further surfaces.
 2. A method of manufacturing an ultrasonic delay line, starting from a glass body two surfaces of which are surface-ground and provided with an input and an output transducer, characterized in that the body is divided into portions, preferably sawn, substantially parallel to the direction of propagation of the ultrasonic vibrations and perpendicular to the surface of said transducers.
 3. A method of manufacturing an ultrasonic delay line comprising the steps of placing molten glass material in a mold having at least two substantially parallel surfaces provided with protuberances, cooling said glass so that a rough glass body showing two substantially parallel surfaces provided with a fluting corresponding to said protuberances is formed, grinding two otHer surfaces of said rough glass body substantially perpendicular to said first mentioned two surfaces, securing an input and an output transducer respectively on said two other surfaces, grinding at least one further surface of said glass body substantially perpendicular to said first mentioned two surfaces to reflect ultrasonic rays emerging from said input transducer to strike upon said output transducer, and bisecting said glass body according to a plane substantially parallel to said first mentioned two surfaces.
 4. An ultrasonic delay line comprising a glass body having two surfaces which are provided with piezo-electric input and output transducers polarized parallel to their contact surfaces wit the glass body, and at least one third reflecting surface which is parallel to the principal direction of propagation of the ultrasonic vibrations which propagate from the input transducer through the glass body to the output transducer, characterized in that the dimension of the body perpendicular to the last-mentioned third surface is smaller than the dimensions of this third surface, that the directions of polarization of the transducers are also chosen to be parallel to this third surface, and that the surface of the glass body opposite this third surface reflecting the ultrasonic scattered radiation is formed as a damping and/or dispersing surface for this scattered radiation.
 5. An ultrasonic delay line as claimed in claim 4, characterized in that it is manufactured of moulded glass.
 6. An ultrasonic delay line comprising a solid ultrasonic wave-transmitting body having first and second surfaces, an input transducer and an output transducer in contact with said first and second surfaces, respectively, for propagating ultrasonic vibrations from the input transducer through the solid body to the output transducer along a main propagation path, said body having a third ultrasonic energy reflecting surface parallel to said main propagation path and a fourth surface opposite said third surface and formed as an energy damping surface for the scattered ultrasonic radiation reflected from the third surface, the dimension of the solid body perpendicular to the third surface being smaller than the dimensions of said third surface, and wherein said transducers are polarized parallel to their respective contact surfaces with the solid body and parallel to the third surface of the solid body.
 7. A delay line as claimed in claim 6 wherein said transducers are composed of piezoelectric material and said solid body is composed of glass.
 8. A delay line as claimed in claim 7 wherein said glass body is rectangularly shaped and said first and second surfaces are the parallel end faces of the rectangular body.
 9. A delay line as claimed in claim 8 wherein a fifth surface of the body that is perpendicular to the first and third surfaces is formed as an energy damping surface.
 10. A delay line as claimed in claim 8 wherein said transducers extend to the intersecting edges of the third surface with said first and second surfaces.
 11. A delay line as claimed in claim 7 wherein said first and second surfaces are at one end of the body and intersect to form an angle, wherein said third and fourth surfaces are parallel to one another and perpendicular to said first and second surfaces, and said body further includes a reflecting flat end surface remote from said first and second surfaces and perpendicular to said third and fourth surfaces.
 12. A delay line is claimed in claim 7 wherein said third surface is arranged to reflect substantially all of the energy impinging thereon and said body dimensions are chosen so that the distance between the third and fourth surfaces is less than the width dimension of the third surface, whereby the delay line exhibits a wide bandwidth. 